A connection housing (also referred to as a header) is necessary for connecting electrode lines to electrical components of a medical implant. Such a connection housing is generally composed of a connection body made of insulating, preferably transparent, material, which may be a plastic material which preferably includes the materials polyurethane (PU), polycarbonate (PC), and/or epoxy resin. In this connection body at least one externally accessible cavity, in each case containing contacts, is provided for accommodating standard plug-in connectors (such as IS-1, DF-1, or IS-4) for the electrode lines. These electrode lines may be cardiac electrode lines, which may be implanted intracardially or in the form of a coronary sinus (CS) electrode, or nerve or epicardial electrode lines. Such electrode lines may also have another form and function.
The contacts in the cavities are designed as elastic sleeves or plug-in connector receptacles in which the plug-in connector of the electrode line may be inserted, and whose shape and location correspond to that of the standard plug-in connectors. If the connection housing is transparent it can be seen from the outside whether an electrode line plug is inserted far enough into the elastic sleeve or into the plug-in connector receptacle of a particular electrical connection.
The electrical contacts are each connected to one or more electrical conductors which are provided for transmitting electrical signals to these electrical contacts so that the signals may be sent via the electrode line plug to the corresponding electrode at the distal end of the electrode line, and thus to the treatment site in the human or animal body. Electrical signals measured in the body may also be sent in the opposite direction in the same manner. It is known from the prior art that these electrical conductors are composed of an electrically conductive metal, preferably metal wires or metal ribbons. The latter are either formed during installation or punched from a preformed sheet metal strip (in blanks) and connected to the electrical contacts using joining processes such as welding, soldering, or crimping. Such a known approach is described in International Patent Application No. WO 01/99239 A2, the disclosure of which is incorporated in its entirety into the present patent application.
The connection housing may include a base body and/or a connection body which are connected to one another in a suitable manner. Any other design known from the prior art is also possible, in particular a multipart design in which the constituent components are individually joined together. Therefore, in the discussion below reference is made only to a connection housing.
The invention further relates to a medical implant, for example an implantable cardiac pacemaker, defibrillator, cardioverter, nerve stimulator, or the like. The medical implant includes a connection body or header, described at the outset, which is fastened to a hollow housing. The hollow housing is hermetically sealed with respect to the surroundings, and is generally made of biocompatible metal. The hollow housing is used to accommodate an electrical circuit or control electronics system composed, among other things, of capacitors, batteries, and other electrical circuitry. The circuit is provided for measuring signals from the human body, sending signals to the human body, or combinations thereof, and it is also suited for transmitting signals to a receiver located outside the body.
The electrical connection of the electrical circuit in the hollow housing to the electrical conductors present in the header, which are electrically connected to the electrical contacts, is generally achieved via filtered or unfiltered hermetically sealed feedthroughs, also known as glass/ceramic housing feedthroughs. Such feedthroughs are known from the prior art, for example from DE 103 29 261 A1, EP 1 148 910 A1, or EP 1 897 589 A2, the disclosures of which are incorporated in their entirety into the present patent application. The feedthroughs are composed of at least one feedthrough pin, and are embedded in a wall of the hollow housing so as to close off the hollow housing with a hermetically tight seal. The feedthroughs may also be implemented as filter feedthroughs in which the filter has an electrical low-pass filtering effect.
Great demands are placed on the quality of a housing for a medical implant. In particular, the hollow housing and the connection housing must interact reliably and remain tightly sealed for years. The connection housing itself must be stable over a long period of time and have a precise fit.
Various approaches are known from the prior art for meeting the requirements described above. For instance, it is known to integrally cast the connection housing directly onto the hollow housing. For this purpose the hollow housing having conductors for the electrical connections which are attached to the feedthrough pins, using a joining process, and the electrical contacts are inserted into a casting mold, and are cast by filling the closed casting mold with liquid plastic. The liquid plastic is allowed to harden in the casting mold, and after removal of the casting mold results in a connection housing which is produced in a single work step and is directly and securely joined to the hollow housing. Another approach known from patent applications EP 1 795 225 A1 or EP 1 795 226 A1 provides for separate manufacture of the connection housing by first casting same as described above in a casting mold together with the electrical conductors and the electrical contacts, and then electrically connecting the leads to the feedthrough pins for the feedthroughs in the hollow housing a joining process. In addition, the connection housing is glued to the hollow housing a suitable liquid or paste adhesive. The disclosures of the two cited patent applications EP 1 795 225 A1 and EP 1 795 226 A1 are hereby incorporated in their entirety into the present patent application.
The feedthrough pins and the electrical contacts are electrically connected to the electrical conductor before the casting operation by use of a joining process. Such a joining process may include a laser welded connection, welding by means other than a laser, soldering, or gluing using an electrically conductive adhesive, wherein this listing is not to be construed as exhaustive.
The manufacture of a connection housing of the type described above is not without risks. For example, defects may result from the primarily manual production of the connection housing. Although the electrical conductors (ribbons or bent-punched parts) may be fabricated with pre-bending in three dimensions, the further processing is not possible by automated means. Thus, the electrical conductors and the contacts must be welded or soldered by hand and then cast. This results in inadvertent errors, for example in the electrical contacting of the contacts to the conductor.
Furthermore, quality and functional control of the connection housing is not possible until after the connection housing has been completely manufactured. Thus, if minor defects are present the entire connection housing may be unusable. Therefore, there is a need for a connection housing or a medical implant which can be manufactured by automated means and which may be easily tested for quality and functionality before final manufacture without complete installation being necessary.